1. Field of the Invention
The present inventuon relates to a method for wrapping bales of fibrous crop materials in a pick-up baler in which cylindrical bales are formed from windrowed fibrous crop materials. When a bale is completed, the free end of a binding twine is projected onto the periphery of the bale by means of a twine-feeding and guiding device. The twine is then hooked onto the bale and is helically wound under tension around the bale while the twine-feeding and guiding device moves at constant speed in parallel to the axis of the bale so as to wrap the whole cylindrical periphery of the bale with the twine. The twine is later cut at the end of the wrapping operation in the median zone of the bale periphery.
2. Related Art
Many of the conventional devices (such as the one in French Pat. No. 2 518 263) have one particular disadvantage which is to leave the ends of the bale unwrapped for a not inconsiderable period of rotation, during which the ends become loose and crumble, thereby causing the twine to become relatively slack in those parts. The loose hay and twine interfere with the operation of the baler.
According to the known method, wrapping of the bale begins in the longitudinal center of the bale periphery, moving toward one end of the bale, and then reversing the direction of movement of the twine-feeding and guiding device, toward the other end of the bale, and then returning toward the starting point of the operation at the first end of the bale. Understandably, with this type of system, one half of the bale is left completely unwrapped for a period of time while during that same period of time the other half of the bale is wrapped twice over. Moreover, the time required to wrap the bale is quite long since for every wrapping operation the twine feeding and guiding device has to move twice along the length of the cylindrical bale.
To overcome these disadvantages, it has already been proposed to deposit the twine on the bale periphery by means of two twine-guiding tubes, of which one end is mounted for pivoting in the axis of the installation, namely in extension of the mediam plane of the bale which is perpendicular thereto, while the other end through which the twine is deposited, sweeps an arc-forming area above the bale which extends from one end of the bale cylindrical periphery to the other. In this case, the binding operation begins at one end of the bale and stops at the other before the twine is cut. When, in such a case, two twine-guiding tubes are used simultaneously, these tubes pivot in opposite directions so that the two ends of the bale are wrapped right from the start of the operation and crumbling of the ends is prevented. The wrapping time, on the other hand, is still quite long and the spacings between two adjacent twine windings vary from one spacing to the other, due to the pivoting movement of the twine-guiding tubes.